Enthalpy heat exchanger with variable recirculation and filtration

Abstract

A heat exchanger for both sensible and latent energy, enthalpy, has walls or plates that extend between two air streams that also permit and assist recirculation and filtration. The walls between air streams consist of a substrate with a coating on the substrate. The coating, in combination with the substrate material original porosity, is used to control final porosity and hydrophilic/oleophilic characteristics. By control of the pore size and surface material characteristics, there can be almost a total recirculation, a recirculation of only gases (filtering out solid particles), a transfer of only moisture and heat, or a transfer of only heat. The pore size and characteristics of the coating along the path of the air streams can be varied so that different types of exchange can be obtained along the path of the air streams.

1. An exchanger for the transfer of heat and moisture comprising:
 two flow paths for air having different temperatures and moisture contents;  
 a common wall separating said two air flow paths and extending along said air flow paths;  
 said common wall having different flow-through characteristics along said air flow paths;  
 said different flow-through characteristics including relatively uniform but different porosity at different areas along said common wall between said air flow paths and different material means resulting in different passage between said two air flow paths for heat, moisture and solids.  
 
   
   
     2. An exchanger for the transfer of heat and moisture as in  claim 1  wherein:
 said wall includes a porous base material;  
 said different porosity includes a complete coating on said wall base material over one area, that renders said wall at least substantially impervious to the transfer of fluid, and an uncoated second area of said wall base material, that is porous to the transfer of fluid.  
 
   
   
     3. An exchanger for the transfer of heat and moisture as in  claim 2  wherein:
 said second area of said wall that is porous to the transfer of fluid has pores that are from 3-10 microns in size so as to transfer air through said wall second area while preventing the transfer of most solid particles.  
 
   
   
     4. An exchanger for the transfer of heat and moisture as in  claim 2  wherein:
 said porous base material is primarily formed from glass fibers;  
 said coating material is primarily formed from polyvinyl alcohol.  
 
   
   
     5. An exchanger for the transfer of heat and moisture as in  claim 1  wherein:
 said wall includes a porous base material;  
 said different porosity includes a complete coating on said wall base material over one area, that renders said wall at least substantially impervious to the transfer of fluid, and a coating over a second area on said wall base-material that includes a material having pores that are from 3 to 100 Angstroms so as to transfer moisture while preventing the transfer of other gasses and solid particles.  
 
   
   
     6. An exchanger for the transfer of heat and moisture as in  claim 5  wherein:
 said material with pores that are from 3 to 100 Angstroms is a desiccant to which moisture is attracted.  
 
   
   
     7. An exchanger for the transfer of heat and moisture as in  claim 6  wherein:
 said desiccant material is selected from the group consisting of a ceramic, clay, activated alumina, activated charcoal, and calcium sulfate.  
 
   
   
     8. An exchanger for the transfer of heat and moisture as in  claim 1  wherein:
 said different porosity at different areas includes a first area with relatively large pores that permit the passage of fluid but prevent the passage of most solid particles, and a second area with relatively small pores that permit the passage of moisture while preventing the transfer of solid particles and other fluids.  
 
   
   
     9. An exchanger for the transfer of heat and moisture as in  claim 8  wherein:
 said large pores are from 3 to 10 microns and said small pores are from 3 to 100 Angstroms.  
 
   
   
     10. An exchanger for the transfer of heat and moisture as in  claim 9  wherein:
 said wall includes a porous base material;  
 said relatively small pores are in a desiccant material in a coating on said porous base material.  
 
   
   
     11. An exchanger for the transfer of heat and moisture as in  claim 8  wherein:
 said different porosity at different areas include a third area with a coating that permits the transfer of heat but that is at least substantially impervious to the transfer of solids and fluids.  
 
   
   
     12. An exchanger for the transfer of heat and moisture comprising:
 two flow paths for air having different temperatures and moisture contents;  
 a common wall separating said two air flow paths and extending along said air flow paths;  
 said common wall having different flow-through characteristics along said air flow paths;  
 said different flow-through characteristics including relatively uniform but different porosity at different areas along said common wall between said air flow paths;  
 said wall includes a porous substrate with a coating;  
 said coating provides said different-porosity at different areas;  
 said coating is incomplete in one area permitting circulation of air through said wall;  
 said coating contains a material having small pores in a second area that permits the transfer of moisture but that prevents the transfer of gasses and solid particles;  
 said coating is complete in a third area transferring heat but at least substantially preventing the transfer of any fluid or solid material.  
 
   
   
     13. An exchanger for the transfer of heat and moisture as in  claim 12  wherein:
 said material having small pores is hydrophilic and can transfer moisture from one said air flow path to the other said air flow path through said common wall by capillary attraction and diffusion while said small pores are small enough that solid particles and non-hydrophilic gasses will not pass through them under normal operating pressures.  
 
   
   
     14. A heat-exchanger with variable recirculation and filtration comprising:
 a porous base web having large openings therein capable of passing gasses therethrough;  
 a first coating on a first area of said porous base web having no pores therein at least substantially precluding the passage of fluids therethrough;  
 a second coating on a second area of said porous base web having small pores therein precluding the passage of gasses but permitting the passage of a liquid.  
 
   
   
     15. A heat exchanger with variable recirculation and filtration as in  claim 14  wherein:
 said porous base web openings are from 3-10 microns in size;  
 said second coating small pores are from 3-100 Angstroms.  
 
   
   
     16. A heat exchanger with variable recirculation and filtration as in  claim 14  wherein:
 said porous base web material is primarily formed from glass fibers;  
 said first area coating is primarily formed from polyvinyl alcohol;  
 said second area coating is a desiccant to which moisture is attracted.  
 
   
   
     17. A heat exchanger with variable recirculation and filtration as in  claim 15  wherein:
 said porous base web material is primarily formed from glass fibers;  
 said first area coating is primarily formed from polyvinyl alcohol;  
 said second area coating is a desiccant to which moisture is attracted.  
 
   
   
     18. A heat exchanger with variable recirculation and filtration as in  claim 16  wherein:
 said second area coating desiccant is selected from the group consisting of a ceramic, clay, activated alumina, activated charcoal, and calcium sulfate that can transfer moisture from one side of said porous base web to the other side of said porous base web by capillary attraction and diffusion while said small pores are small enough that solid particles and non-hydrophilic gasses will not pass through them.  
 
   
   
     19. A heat exchanger with variable recirculation and filtration as in  claim 14  wherein:
 said second coating on a second area of said porous base web is a polymer containing a porous hygroscopic material selected from the group consisting of polyvinyl alcohol, polyacrylamide, polyacrylate, polyethylene glycol, polypropylene glycol, polyurethane, nitrilephenol, alkyd-based resins and water based acrylics.  
 
   
   
     20. A heat exchanger with variable recirculation and filtration as in  claim 14  wherein:
 said porous base web is supported by a reinforcement means.